"The Invisible Tool"/beat rates - and where they come from

Michael Gamble michael@gambles.fsnet.co.uk
Mon, 20 Oct 2003 16:27:02 +0100


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Hello list
Like all of you, I imagine, I was first made aware of these beats when =
listening to a piano (in my case pipe organ) being tuned. My curiosity =
led me to analyse the reason and I turned to simple mathematics for the =
answer. Enter my "small equation" where the fundamental (1st.Harm.) is =
multiplied by the 12th. root of 2 to derive the next fundamental in the =
ascending equal tempered chromatic scale. (Simply devide if you want to =
go down chromatically). In every case the resultant becomes a =
Fundamental Note - or 1st.Harmonic. I know this is all "old hat" but =
there's probably some meat in it to be chewed over just the same. Now =
taking the Fundamental and multiplying by "Two" one gets the second =
harmonic. Multiplying by "Three" gets the third harmonic ad. inf. The =
really interesting point now comes... Take your M10 based on A# (which =
computes at 466.16376.....)The 5th. harmonic of that A# =3D =
2796.9826...... the M10 is F(which computes at 1396.9129.......) The =
2nd. harmonic of that                          F =3D2793.8259...... =
There we have a difference of 3.1567..... Hz which is the beat you hear. =
The same applies, of course, to any and all intervals in the equal =
tempered scale, be they M3,M4,M5 - whatever.
It is interesting to apply that "small formula" to log all the notes of =
the equal tempered scale on a mathematical basis and thereby to extract =
the "Beat-rate" information whole-sale. To me this information is "an =
invisible tool" - and I use it - as do you. But it's nice to see an =
invisible friend sometimes!=20
Of course! There are many pitfalls! Many pianos do not produce the exact =
mathematical frequencies according to my table. Those times when the =
first covered (wrapped) Bass string are played with their M10 - and the =
beat rate does not conform to the mathematical progression of the tables =
as produced in the "metals" section of the piano. Well..., That's life =
:-)  I find the "scientific calculator on the PC best as it produces so =
many decimal places! In using such a calculator you can go right up the =
scale and land up, an 8ve later with exactly twice the number you =
started out with. Now that's Magic!=20
Regards
Michael G (UK)
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